Conformationally Mobile Glucosylthioureidocalix[6]- and Calix[8]arenes: Synthesis, Aggregation and Lectin Binding

Abstract

Two new glucoclusters 2a and 2b, in which the sugar units are connected to the upper rim of methoxycalix[6]- and calix[8]arene derivatives via thiourea linkages, were synthesised and their aggregation properties in water studied by 1H NMR, atomic force microscopy and dynamic light scattering. Small size aggregates (2–10 nm diameter) are formed by both macrocycles, which become much larger (200–300 nm) in the presence of a phosphate buffer, whereas other anions have no effect. The glycoclusters 2a and 2b interact with plasmid DNA but do not condense it, while in the presence of a glucose-specific lectin such as Concanavalin A (ConA) agglutination occurs. The data obtained give useful insights into the mode of binding of calixarene-based glycoclusters with lectins. The self-aggregation properties in water solution of glucosylthioureidocalix[6]- and [8]arenes were studied by a combination of different techniques. These glycocalixarenes showed a specific interaction with phosphate ion and ConA evidenced by an increase of the aggregate sizes from 3 to 10 nm up to 200–300 nm diameter.